Check valves that allow fluid to flow out in only one direction and prevent the reverse flow have been known in the past, and various types such as a ball type, swing type, lift type, and disk type according to the structure of a valve have been known. A purpose of the check valve is to prevent the reverse flow of fluid, and since overall the body is not complicated, such as the disk type, it can be provided at a low cost, is easily installed in the middle of a tubular body, and therefore it is suitable for disposing, for example, in a fuel passage of a carburetor or the like.
Further, a disk type check valve forms an inflow opening and an outflow opening by a casing as described in, for example, Japanese Unexamined Patent Application Nos. H10-288265 and H07-101066, and a ring-shaped valve seat is formed there between to dispose a disk-shaped valve body having a larger diameter than the outflow opening and a smaller diameter than the valve seat, that is biased in the outflow opening direction by a coil spring. When the fluid flows in from the inflow opening at a pressure exceeding the biasing force of the coil spring, the valve body slides in the outflow opening direction by a large pressing force larger than the biasing force of the coil spring acting on the valve body so that the fluid that is coming in from the inflow opening through a gap which is formed on the outer periphery of the valve body in the valve seat, flows out. Conversely, when the fluid reverse flows from the outflow opening direction, the valve body slides in the inflow opening direction by the biasing force of the coil spring to close the inflow opening so as to prevent the reverse flow of the fluid.
A check valve using a further simple disk-shaped valve body described in Japanese Unexamined Patent Application No. 2010-60110 has also been known. This check valve 330, as illustrated in FIG. 5A, is configured such that a valve body 332 and a valve seat 336 are inserted to attach in a valve holder 320, and assembled by engaging a projecting part 324 to a groove 338 of the valve body 332. With this check valve 330, as illustrated in FIG. 5B, the valve body 332 becomes an open state by abutting onto a valve stopper 326 made from a curved longitudinal beam member, and also becomes a close state by abutting the valve body 332 onto a valve seat 336 by reverse direction pressure.
Therefore, there is a large difference in the check valves described in Patent Application Nos. H10-288265 and H07-101066 in that an advantageous effect is exhibited with a simple structure without using means for pressing the valve body against the valve seat, for example, such as a coil spring.
Furthermore, a check valve illustrated in FIGS. 6A, 6B and 6C is a conventionally known check valve having a further simpler configuration than the check valve that exhibits the similar advantageous effect with a simple structure without using biasing means illustrated in FIGS. 5A and 5B. It is configured such that a case body 1 made of, for example, aluminum die cast, with a cylindrical inflow opening 2 and an outflow opening 3 formed respectively in both ends, as well as a cylindrical valve seat 4, having a predetermined length, is formed in the axial direction between the inflow opening 2 and the outflow opening 3A disk-shaped valve body 5 with an outer diameter having a slightly smaller diameter than the inner diameter of the valve seat 4 as well as a larger diameter than the inner diameter of the inflow opening 2, is disposed with an ability to move in the axial direction of the valve seat 4, and a support member (retainer) 6 for the valve body 5 that is disposed between the outflow opening 3 of the valve seat 4 and the valve body 5.
Moreover, the support member (retainer) 6 is configured as illustrated in FIGS. 7, 8A, 8B and 8C where a disc-shaped base seat 61 that forms an outflow window 62 in the center is fit into a circular circumferential groove formed between the outflow opening 3 and the valve seat 4 as illustrated in FIGS. 6A, 6B and 6C. Support pieces 64 for the valve body 5 illustrated in FIGS. 6A, 6B and 6C are provided in an upwardly projecting manner (the valve body 5 direction) in an open edge 63 of the outlet window 62 formed in the center of the base 61, as illustrated in FIGS. 7, 8A, 8B and 8C.
Also, in a check valve according to the present embodiment, as illustrated in FIG. 6A, a predetermined gap 41 is formed between the top surface 43 of the valve seat 4 and the valve body 5 because the valve body 5 disposed in the valve seat 4 is pressed in the outflow opening 3 direction by the fluid normally entering from the inflow opening 2 to be supported by the support pieces 64 of the support member (retainer) 6.
Accordingly, the fluid entered from the inflow opening 2 flows towards the outflow opening 3 from the inflow window 62 of the support member (retainer) 6 via a space 42 formed between an inner peripheral surface 44 of the valve seat 4 and the support piece 64 from the gap 41.
When the flow of the fluid changes in this condition, in other words, when the fluid that has been flowing toward the outflow opening 3 flows in reverse and flows in the direction of the inflow opening 2, the open end 21 of the inflow opening 2 is closed by moving the valve body 5 in the axial direction within the valve seat 4 because the fluid that has been flowing toward the outflow opening 3 flows in reverse to operate the check valve. That is, as illustrated in FIG. 6B, the valve body 5 tightly contacts the open end 21 area of the inflow opening 2 of the valve seat 4 due to the fluid pressure of the reverse flow and the check valve becomes the close state.